1. Field of Invention
The present invention relates to sealing members.
2. Description of Prior Art
Prior patents, such as U.S. Pat. No. 3,970,321 have been directed to forming a seal in an annulus between a longitudinally movable shaft and a housing containing the shaft. The structure described in this patent included a two piece elastomer member including a cup packing and a pressure distributing ring. An end extension ring was formed on a front face of the cup packing to assist in prevention of extrusion of the elastomer member. However, an annular gap was present between the cup packing inner surface and the shaft behind the extrusion ring. Since the cup packing was structured to bend inwardly along the inner surface into increased contact with the shaft as pressure increased, the possibility of elastomer extrusion past the extrusion line was present.
Another U.S. Pat. No. 2,509,436, involved a packing for sealing between a shaft and a housing. However, although metallic reinforcing rings were in some instances provided, a space was left between the reinforcing ring and the shaft. This space permitted the possibility of elastomer creep or flow in high pressure situations.
Other patents known to applicants also relating to forming a seal between a shaft and a housing are U.S. Pat. Nos. 4,053,166; 4,201,392; 2,867,457 and 2,509,151. However, so far as is known, these references did not teach structure for protection against elastomer extrusion at high sealing pressures.